In the course of its existence, a bacterium may transit through many different locations, both in the external environment and within an animal host. Bacteria have the ability to sense a multitude of environmental stimuli and use these cues to regulate gene expression and adapt accordingly. Temperature is one of the many signals in the environment bacteria use as a cue for regulating gene expression. For mesophilic organisms, the most well studied are the reactions to temperatures at the border of growth for these bacteria- the heat (42[unreadable]C) and cold shock (15[unreadable]C) responses. Surprisingly, what has been less well studied is the response of bacteria to temperatures they might normally encounter in the human host (body temperature-37[unreadable]C) and in external settings inhabited by humans (room temperature- 20[unreadable]C-23[unreadable]C). We propose to use molecular biology approaches to explore the short-term response of both commensal and pathogenic strains of Escherichia coli to these temperatures. Studies will be completed to characterize the changes that occur primarily in the first minutes to hours after a temperature shift, mimicking the movement of a bacterium between host and external environments. These may offer intriguing insights of the timeframe and genes required for adaptation to these settings that may be particularly relevant to infection and transmission. Focused temperature shift studies on discrete sets of thermo regulated genes in commensal and pathogenic strains of E. coli (fimbrial, attachment, iron acquisition, amino acid utilization, and stress response) will yield data on how rapidly bacteria adapt to temperature changes, and expand our understanding of the relative importance of temperature to the regulation of these individual genes. The completion of these studies in uropathogenic and enteropathogenic E. coli in addition to E. coli K-12 will determine if a conserved response to temperature is maintained within the genus, thus broadening its potential relevance. These studies will also serve as the foundation for genome-wide studies to assess the global role of temperature on gene expression, thoroughly characterizing the early responses in both E. coli K-12 and CFT073. Characterization of the response of E. coli to intermediate temperatures between 23[unreadable]C and 37[unreadable]C and at 40[unreadable]C, indicative of a host fever response, will uncover what temperature ranges program a characterized thermoregulatory response. PUBLIC HEALTH RELEVANCE: The proposed research provides basic knowledge regarding the contribution of temperature to gene regulation in communal and pathogenic strains of Escherichia coli. Identification of the bacterial genes more highly expressed at human body temperature (37[unreadable]C) could yield valuable anti-infective targets for chemotherapeutic drugs or vaccines that would decrease the ability of bacteria to compete and survive within the host. A more thorough understanding of the adaptation of E. coli to ambient indoor room temperatures (20[unreadable]C-23[unreadable]C) may identify proteins or processes that facilitate survival in the environment that can be targeted for prevention or disinfection purposes.